Strong social networks (e.g., family, friends, and acquaintances) exert positive effects on older adults' emotional, cognitive, and physical health. Social engagement theory suggests that interacting with close ties and social groups leads to everyday activities that benefit health. Yet, gaping holes remain in understanding how social networks foster well-being via interactions and behaviors in daily life. Different social partners may serve complementary functions. The proposed study addresses three important questions: 1) Do older adults who report a greater variety of social ties engage in more diverse social interactions throughout the day? 2) Do social partners serve distinct global (e.g., social support) and daily functions (e.g., conversations and physical activity throughout the day)? 3) Are these patterns of social networks and activities associated with daily and overall well-being? The proposed study includes an initial interview assessing global properties of close ties and well-being and daily processes among older adults (N = 300). The study will use cutting edge modes of data collection throughout the day over four days: self-reports of social interactions collected via handheld computers, recorded conversations (via electronically activated recordings, EAR), and physical activity measured via actigraphs. The proposed research will address older adults' social, emotional, cognitive, and physical experiences in the following three aims: Aim 1 will examine links between reports of the social network and social partners encountered in daily life. Individuals who report large social networks may interact with some of those social partners on a daily basis, but also report ties to social partners with whom they have infrequent contact. The study considers several modalities of contact (phone, in person, text). Aim 2 will assess how daily social interactions (incorporating relationship type, intimacy of tie, variety of interactions) are associated with daily cognitive, physical, and emotional experiences. A functionalist perspective suggests different social partners serve distinct functions. Aim 3 will examine associations between social networks, daily experiences, and daily well-being and global well-being. Interacting with a variety of social partners may be beneficial for daily mood, and physical symptoms. We also ask whether daily activities (e.g., conversations, physical activity) mediate associations between social networks and well-being. Across aims, we will consider correlates of social networks and daily activities: socioeconomic status (SES), gender, and age. Innovation and impact: Prior research has relied primarily on self-reports of close partners. This study will provide a novel investigation of how such reports are associated with daily social interactions, physical activity, and cognitive activity in everyday life. Researchers have documented the critical role of social ties on health for over three decades, but the proposed study will be the first to examine how social partners contribute to emotional, physical and cognitive experiences and to daily and global well-being. This study sets a stage for future longitudinal follow up of these participants and important information aimed at improving the social lives of older adults.